I am the same exact way. I get amazingly enraged at just hearing a specific person's name. I adopt the mood of whoever I'm talking to, but the second I change who I'm talking to my mood changes as well. Everything seems to affect my moods and usually it's to piss me off.

Unfortunately, there's no quick/good answer.

Most importantly, see a therapist specifically to work on skills for the issues. Once you have skills to deal with the day-to-day issues, you can work with them on the bigger picture stuff.

For me, I'm finding small things that work. I found a small chain tassel at the craft store that I keep in my pocket and when I see that I'm starting to get pissed or overwhelmed by my emotions, I'll just start feeling the chains in my pocket. It sort of helps ground me.

So far I haven't found anything to help the whole adopting someone else's mood thing. But that's a whole lot easier for me to deal with than the tidal wave of emotions. The problem is, once those emotions start to overwhelm me, anything and everything sets me off. If I can find a way to stop the emotions from becoming overwhelming, I think things can become much more manageable.